Infrared nonlinear optical performances of a new sulfide β-PbGa2S4

Abstract

Nonlinear optical (NLO) crystals can produce tunable lasers through the direct second-harmonic generation (SHG) process, which is of great significance in modern laser technology. Herein, a new chalcogenide β-PbGa2S4 (1) crystallized in space group of Pna21 was synthesized via high-temperature solid-state reactions. Compound 1 is composed of a three-dimensional framework [Ga8S16]8− with hexagonal voids filled by Pb atoms via covalent Pb–S interactions. Importantly, it exhibits promising NLO performances, such as phase-matchable SHG efficiency (0.6×AgGaS2@1200 nm and 0.1×AgGaS2@1910 nm), moderate band-gap (2.46 eV), suitable laser-induced damage threshold (3.0×AgGaS2), and a broad IR transparency window (0.5–25.0 µm). SHG response of 1 is mainly attributable to the occupied S–3p and Ga–4p states and unoccupied S–3p and Pb–6p states.